In one configuration, Electro-optic modulator (EOM) is a signal-controlled Mach-Zehnder interferometer generating ultra-fast optical signals over optical fiber communication systems. In such an EOM, the input continuous optical wave is split in two halves at a 3 dB Y waveguide branch. Optical wave in each branch experiences a phase change. The two branches will then be connected and recombined using a second Y-shaped waveguide branch. At the output Y waveguide branch two split waves are recollected, so that if two split guided waves are in-phase, they will constructively interfere resulting in the on-state in the optical switch (or modulator). While in 180° phase difference the destructive interference leads to the off-state. A signal-controlled electro-optic material imbedded in one of the two branches is responsible for enforcing phase difference in the interferometer.
Three types of nonlinear electro-optic materials may be used as the switching component of the EOMs; Lithium Niobate (LiNbO3), Gallium Arsenide (GaAs), and Indium Phosphide (InP). Recently organic chromophore-doped polymers have been implemented as the switching component, due to their cost-effective production process and their faster electro-optic effect. Despite dazzling progress in EOMs, they have tremendously high loss (4˜9 dB) as a result of their unavoidable waveguide loss and mismatch between on-chip waveguides and external optical fibers. Furthermore, due to complicated engineering process of gigabit-speed modulators, they failed to be cost-effectively manufactured, particularly those composed of more than one Mach-Zehnder interferometer.